Spam, an electronic version of junk mail, is unsolicited email on the Internet. A filter, on the other hand, is a piece of software that is capable of identifying an email message as spam and blocking or redirecting delivery of a spam message. Some existing methods for generating spam filters rely on collecting spam email messages, processing the messages, and creating filtering rules to be later used to detect spam email.
Presently, there are products that are capable of filtering out unwanted messages. For example, a spam block method exists which keeps an index list of all spam agents (i.e., companies that generate mass unsolicited e-mails), and provides means to block any e-mail sent from a company on the list.
Another “junk mail” filter currently available employs filters that are based on predefined words and patterns as mentioned above. An incoming mail is designated as an unwanted mail, if the subject contains a known spam pattern.
However, as spam filtering grows in sophistication, so do the techniques of spammers in avoiding the filters. Examples of tactics incorporated by recent generation of spammers include randomization, origin concealment, and filter evasion using HTML.